Description du sujet de thèse

Influence of non-conservative particle-wall interactions on colloidal organization and transport

An important key to understanding the spatial organization of micro and nanoscale objects near interfaces —whether colloids, marcomolecules or others— is the Gibbs-Boltzmann distribution. Typically, a conservative interaction, say electrostatic or van der Waals, varies as a function of the distance from the wall and thus determines the spatial organization there. Besides this quasistatic distribution, advective transport of the objects can be greatly impacted by such distributions because the spatial dependence of the velocity profile couples to that of the Boltzmann distribution – the probability of having a certain velocity and thus a given displacement over some time is given by the probability of being in a certain position in space [1].
In this generalized organization and transport context, hydrodynamic interactions between particles and bounding walls open a new way of controlling spatial organization, and thus the near-surface transport, of colloidal objects. The non-equilibrium interactions of interest here are typically lift-like, velocity-dependent forces that may arise due heterogeneity of the substrate or the mixture, softness, or electrokinetics. These intrinsically non-equilibrium interactions, however, are not very well understood experimentally, and including them into a statistical theory is a challenge. Nevertheless, such non-equilibrium interactions may be important in, for example, all of microscale biology, wherein most objects are of colloidal scale, interfaces are never far away, and the fluids are highly complex.
In this mainly experimental thesis, the student will study the near-wall organization and dynamics of colloidal particles in complex non-equilibrium situations. The main experimental technique to be used during the project is a total internal reflection fluorescence microscopy (TIRFM, also called evanescent-wave microscopy) in conjunction with microfluidics to control the flow. While familiarity with the specific TIRFM technique or microfluidics is not required, a background with some combination of experimental physics, hydrodynamics, soft matter, and/or statistical physics will be advantageous to the successful candidate for the position. Besides, specific experience in optics or microscopy, image analysis, and data processing and/or mathematical modelling would be useful. Above all, we seek a motivated, hard-working, team-playing and curious student to join a supportive, active and interdisciplinary team.
The PhD is set to begin in late 2025 and is fully funded by the European Research Council within the context of a Consolidator grant held by the PI. The student will be part of the Gulliver Laboratory, working in the center of Paris, France, at the IPGG Microfluidics Institute, and at the ESPCI – PSL University. Interested candidates are encouraged to send a motivation letter specific to the project, CV and the contact information of references to the PI.

Contexte de travail

We are theorists and experimentalists working at the interface of physics, chemistry, biology and computer science. Our research focuses on soft matter (colloids, polymers, liquid crystals, granular matter, thin sheets...), active matter (self-propelled colloids, swimming droplets, walking grains, swarms of robots... ) and molecular systems (DNA, RNA, enzymes...). We study various aspects of these systems such as topology, self-assembly, interfaces, information processing, evolution..., while also developing general theoretical methods. The name Gulliver captures the diversity of scales that are studied in the lab.

Contraintes et risques

Work in laboratories where the use of a chemistry hood is a possibility